Conditional choices and defaults

[Dan Haywood]

Folks,
just to let you know of a new (rather overdue) feature that I've just
committed [1], which is the ability to set up conditional choices and also
defaults.

Examples are:
- category/subcategory... where the subcategory depends on the parent
category, or
- country/state ... where the state depends on the country.

You can see an example of the first in Isis ToDo app [2], eg:

public ToDoItem updateCategory(
            final ToDoItem item,
            final @Named("Category") Category category,
            final @Named("Subcategory") Subcategory subcategory) {
        item.setCategory(category);
        item.setSubcategory(subcategory);
        return item;
    }

    public Category default1UpdateCategory(
            final ToDoItem item) {
        return item.getCategory();
    }
    public Subcategory default2UpdateCategory(
            final ToDoItem item) {
        return item.getSubcategory();
    }

    public List<Subcategory> choices2UpdateCategory(
            final ToDoItem item, final Category category) {
        return Subcategory.listFor(category);
    }


Note how the choices method now takes parameters; it can therefore see the
current value of the category.

Similarly, you can see an example fo the second in Estatio [3], eg:

    public CommunicationChannelOwner newPostal(
            final @Named("Owner") CommunicationChannelOwner owner,
            final @Named("Type") CommunicationChannelType type,
            final Country country,
            final State state,
            final @Named("Address Line 1") String address1,
            final @Named("Address Line 2") @Optional String address2,
            final @Named("Postal Code") String postalCode,
            final @Named("City") String city) {
        communicationChannels.newPostal(owner, type, address1, address2,
postalCode, city, state, country);
        return owner;
    }
    ...
    public CommunicationChannelType default1NewPostal() {
        return choices1NewPostal().get(0);
    }
    public Country default2NewPostal() {
        return countries.allCountries().get(0);
    }
    public List<State> choices3NewPostal(
            final CommunicationChannelOwner owner,
            final CommunicationChannelType type,
            final Country country) {
        return states.findStatesByCountry(country);
    }
    public State default3NewPostal() {
        return states.findStatesByCountry(default2NewPostal()).get(0);
    }

Here the type is an entity.

~~~
When I was doing the checkin, I realized that I haven't implemented
validation checking.  So I've descoped it.  It isn't actually an issue if
you have choices, because it isn't possible to enter any other value
anyway.  But in the more general case I can see this might be needed.  If
anyone discovers a need, raise a new ticket.

Cheers
Dan


[1] https://issues.apache.org/jira/browse/ISIS-478
[2]
https://github.com/apache/isis/blob/52bc369a0906a900fbbddf3cd7ae610d75b987a3/example/application/quickstart_wicket_restful_jdo/dom/src/main/java/dom/todo/ToDoItemContributions.java#L166
[3]
https://github.com/estatio/estatio/blob/3bb6e8d1a80b512a5fadf6a0f6268405a81cbbe8/dom/src/main/java/org/estatio/dom/communicationchannel/CommunicationChannelContributedActions.java#L71